Reduce time thresholds for purging GrContext resources to 15s.

These were initially set to 30s. However, memory usage on perf bots was
not reduced to the previous values from before the GrContext flush count
mechanism was removed.

Bug: 883507
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Iccf8c622f1aa3c2592e0f3f147a772878d7f8e72
Reviewed-on: https://chromium-review.googlesource.com/1236175Reviewed-by: Eric Karl <ericrk@chromium.org>
Commit-Queue: Brian Salomon <bsalomon@google.com>
Cr-Commit-Position: refs/heads/master@{#593489}

components/viz/common/gpu/context_cache_controller.cc

@@ -16,7 +16,7 @@
 namespace viz {
 namespace {
 static const int kIdleCleanupDelaySeconds = 1;
-static const int kOldResourceCleanupDelaySeconds = 30;
+static const int kOldResourceCleanupDelaySeconds = 15;
 }  // namespace
 
 ContextCacheController::ScopedToken::ScopedToken() = default;

gpu/command_buffer/service/gr_cache_controller.cc

@@ -29,7 +29,7 @@ void GrCacheController::ScheduleGrContextCleanup() {
   if (!purge_gr_cache_cb_.IsCancelled())
     return;
 
-  constexpr int kOldResourceCleanupDelaySeconds = 30;
+  constexpr int kOldResourceCleanupDelaySeconds = 15;
   // Here we ask GrContext to free any resources that haven't been used in
   // a long while even if it is under budget. Below we set a call back to
   // purge all possible GrContext resources if the context itself is not being